Pyruvate Dehydrogenase Complex and Citric Acid Cycle
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Glycolysis is the start of the oxidation process of glucose, and one of the end products of that process is pyruvate. Although glycolysis produces energy in the form of ATP, pyruvate is also a high-energy molecule that can be oxidized down further to release more energy.
The first of these processes that oxidizes pyruvate is the pyruvate dehydrogenase complex, which is an enzyme complex located in the mitochondrial matrix. Recall that glycolysis occurs in the cytosol of eukaryotic cells. In this way, the pyruvate produced by glycolysis must first be transported into the mitochondrial matrix in order to be used by the pyruvate dehydrogenase complex. The pyruvate dehydrogenase complex decarboxylates and oxidizes pyruvate to form acetyl-CoA and carbon dioxide. It is important to note that this reaction, called oxidative-decarboxylation, occurs in several other steps of cellular respiration. Remember, whenever something is oxidized, something else is reduced. In the case of the oxidation of pyruvate to acetyl-CoA, NAD+ is reduced to NADH.
In this way, through the pyruvate dehydrogenase complex, more energy in the form of NADH is released. The acetyl-CoA produced is the starting material for the citric acid cycle, which will be discussed elsewhere. As glycolysis breaks a molecule of glucose into two molecules of pyruvate, two molecules each of NADH and acetyl-CoA are produced from each glucose molecule. In this process, one of the three carbons from pyruvate is lost as carbon dioxide. Since there are two pyruvate molecules, two carbons are lost from glucose. As mentioned earlier, the acetyl-CoA produced by the oxidation of pyruvate feeds into the citric acid cycle. The citric acid cycle also occurs in the mitochondrial matrix, and it will complete the oxidation of the acetyl group to form two molecules of carbon dioxide. By the end of the citric acid cycle, all six carbons in the original glucose molecule have been oxidized to form six molecules of CO2.
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Glycolysis is the start of the oxidation process of glucose, and one of the end products of that process is pyruvate. Although glycolysis produces energy in the form of ATP, pyruvate is also a high-energy molecule that can be oxidized down further to release more energy.
The first of these processes that oxidizes pyruvate is the pyruvate dehydrogenase complex, which is an enzyme complex located in the mitochondrial matrix. Recall that glycolysis occurs in the cytosol of eukaryotic cells. In this way, the pyruvate produced by glycolysis must first be transported into the mitochondrial matrix in order to be used by the pyruvate dehydrogenase complex. The pyruvate dehydrogenase complex decarboxylates and oxidizes pyruvate to form acetyl-CoA and carbon dioxide. It is important to note that this reaction, called oxidative-decarboxylation, occurs in several other steps of cellular respiration. Remember, whenever something is oxidized, something else is reduced. In the case of the oxidation of pyruvate to acetyl-CoA, NAD+ is reduced to NADH.
In this way, through the pyruvate dehydrogenase complex, more energy in the form of NADH is released. The acetyl-CoA produced is the starting material for the citric acid cycle, which will be discussed elsewhere. As glycolysis breaks a molecule of glucose into two molecules of pyruvate, two molecules each of NADH and acetyl-CoA are produced from each glucose molecule. In this process, one of the three carbons from pyruvate is lost as carbon dioxide. Since there are two pyruvate molecules, two carbons are lost from glucose. As mentioned earlier, the acetyl-CoA produced by the oxidation of pyruvate feeds into the citric acid cycle. The citric acid cycle also occurs in the mitochondrial matrix, and it will complete the oxidation of the acetyl group to form two molecules of carbon dioxide. By the end of the citric acid cycle, all six carbons in the original glucose molecule have been oxidized to form six molecules of CO2.
MEDSCHOOLCOACH
To watch more MCAT video tutorials like this and have access to study scheduling, progress tracking, flashcard and question bank, download MCAT Prep by MedSchoolCoach
IOS Link: https://play.google.com/store/apps/de...
Apple Link: https://apps.apple.com/us/app/mcat-pr...
#medschoolcoach #MCATprep #MCATstudytools
4 سال پیش
در تاریخ 1399/06/18 منتشر شده
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